The term millennialism comes from the Latin mille anni, which means “a thousand years.” Within Christianity, millennialism is the teaching that Jesus will have an earthly reign of one thousand years on earth. Millennialists differ as to whether the earthly reign of Christ precedes or follows the second coming. Postmillennialism, which has largely died out today, teaches that Jesus will come at the end of the thousand years. Premillennialism, which is popular among most fundamentalists today, teaches that the thousand years begin with Jesus’ Second Coming, which, according to their teaching, immediately follows a seven-year period called the tribulation. Premillennialists can be further divided into three camps: post-tribulationists, who teach that Christians will go through the tribulation, mid-tribulationists, who teach that Christians will go through half of the tribulation, and pre-tribulationalists, who argue that Christians will not go through the tribulation at all.
In the early centuries, millennialist teachings entered the Church through the Zealot party of Judaism. The Zealots expected a military Messiah who would rule the world for a thousand years, with his capital at Jerusalem. In the second century, a new convert named Montanus claimed to be a special emissary of the Holy Spirit. He announced that the New Jerusalem would shortly descend from heaven into a town in Phrygia. Montanus thus became the first Christian date-setting millennialist with a large following. Montanus’ most famous follower was Tertullian, one of the early Church Fathers, but according to St. Augustine, Tertullian later left the Montanist movement and returned to orthodox Christianity. In AD 230, the Synod of Iconium declared that baptisms performed by the Montanist sect were invalid. The Council of Constantinople in AD 381 supported the Synod of Iconium and further declared millennialism to be a heresy—not just because of Montanus, but because of other heretical teachers, such as Apollinarius, so it was a general rejection of millennialism, not just of Montanus’ teachings. Because millennialists used Revelation to support their claims—although Revelation contains no statement that Jesus will reign on earth for a thousand years—the Church was slow to accept Revelation as scripture. To this day, Orthodox churches do not use Revelation for scripture readings during worship. End-times groups have sprung up periodically throughout history, presenting the Church with massive pastoral problems when the end-times prognosticators finally fail. This has kept the historic Church on guard against end-times preachers.
The Protestant Reformers, with the exception of Calvin, all considered millennialism to be a heresy. They needed to deal with the issue, because the Protestant Reformation came right on the heels of a period of end-times hysteria that ended in disappointment. (Calvin made no statement on the issue—the issue was not current in his day, and he was incidentally the only Protestant Reformer who was not clergy.) Lutherans are explicitly forbidden to be millennialists, theoretically on pain of excommunication.
Modern millennialism is largely based on the teachings of John Darby, who lived in the nineteenth century. He was a disaffected Anglican priest who left the Church of Ireland and joined the Plymouth Brethren. He was either the author or the most effective promoter of dispensationalism, of which millennialism is an important part. The Plymouth Brethren spread the doctrine through fundamentalist churches, who at the time were unaware of Apollinarius, Montanus, the Synod of Iconium, the Council of Constantinople, and the position of the Protestant Reformers.
At present, millennialism is strongly rejected as a heresy by Orthodox churches and somewhat less strongly by Lutheran churches. Millennialism is tolerated in most other churches, where it is a minority view, but they consider it more a pastoral problem than a heresy. Millennialism is the majority view in fundamentalist churches, which often consider millennialism to be a test of orthodoxy and sometimes even a prerequisite for membership. Modern millennialists argue that only the Montanist form of millennialism was rejected by the Council of Constantinople, that their doctrine is not the millennialism that the early Church and the Reformers rejected, and they cite Christian authors in antiquity to support this view—most of whom were considered heretics in their own age. Modern millennialists used to be quite passionate about their viewpoint, but over the last few decades, they have become more tolerant of historically orthodox teachings about end times, which they term amillennialism. This tolerance probably stems from the fact that the modern millennialist system, like its historical antecedents, has repeatedly failed in its interpretation of world events.